T REACTIONS OF ALBUMINOUS SUBSTANCES 9 



this reaction we owe to Hopkins and Cole, 1 who showed that the 

 reaction is not due to acetic acid, but to glyoxylic acid, COOH CHO, 

 which is usually present in acetic acid. To get the best results they 

 proceed thus : Glyoxylic acid is prepared by throwing some sodium 

 amalgam into a strong solution of oxalic acid, and then filtering after 

 the formation of gas has ceased. On adding some of this glyoxylic 

 acid to an albumin solution, shaking up, and then adding strong sul- 

 phuric acid, a beautiful bluish-violet colour is seen. The reaction 

 depends, as Hopkins and Cole 2 have also shown, on tryptophane or 

 indol-amino-propionic acid. Tryptophane possesses two other colour 

 reactions, which are, however, only given when it is in the free state, 

 and not as long as it forms part of the albumin molecule. These two 

 reactions are, firstly, a violet colour with chlorine water or bromine 

 water in a solution of acetic acid, and secondly, the pyrrol reaction. 

 (See p. 54.) [That tryptophane also gives the xanthoproteic re- 

 action has been pointed out above.] 



7. The Reaction of Liebermann and Cole 



Liebermann 3 found albumins which had been purified and defatted 

 by four alternate changes of alcohol and ether and then dried, to 

 exhibit a deep blue or bluish-violet colour on being boiled with fuming 

 hydrochloric acid. 



This reaction Hofmeister 4 considered to be a f urfurol reaction in 

 which both the carbohydrate radical of the albumin molecule changed 

 into f urfurol by the action of the acid and the aromatic oxyphenyl 

 radical took part. Cole, 5 however, has shown that Liebermann's reaction 

 is due "to an interaction between the glyoxylic acid which is present in 

 the ether used for washing the albumin, and the tryptophane which is 

 split off from the albumin by the action of concentrated hydrochloric 

 acid." 



8. The Diazo-Readim of Ehrlich and Pauly 



Ehrlich 6 showed in 1882 that urine gives a very distinct red 

 colour during certain pathological changes, for example during typhoid. 

 If one litre of urine is mixed with 50 ccm. of hydrochloric acid and 1 grm. 

 of sulphanilic acid, and if then to 250 ccm. of this mixture 5 ccm. of a 

 half per cent solution of sodium nitrite are added, there is formed, 



1 F. G. Hopkins and S. W. Cole, Proc. of the Royal Soc. 68. 21 (1901). 



2 F. G. Hopkins and S. W. Cole, Journ. of Physiol. 27. 418 (1901). 



3 L. Liebermanu, Zentralbl. f. d. medizin. Wiss. 1887, p. 371. 



4 F. Hofmeister, Leitfaden f. d. praktisch-chemischen Unterricht d. Mediz. p. 80. 

 Braunschweig, 1899. 



v 5 Sydney W. Cole, Journal of Physiology, 3O. 311 (1904). 

 6 P. Ehrlich, Zeitschr. f. klinische Med. 5. 285 (1882). 



